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8723101 
Journal Article 
Efficient routes for the synthesis of 1,4,7,10,13-pentaazacyclohexadecane- 14,16-dione 
Da Pieve, C; Medina-Molner, A; Spingler, B 
2007 
1 
Synthesis
ISSN: 0039-7881
EISSN: 1437-210X 
5 
679-682 
English 
The synthetic access to 1,4,7,10,13-pentaazacyclohexadecane-14,16-dione was significantly improved from an overall yield of 1% to 33%. The procedure involved the use of COCF3 or DDE as highly selective protecting groups for primary amines and of Boc to protect the secondary amine functions. The reaction of a tris-Boc protected tetraethylenepentamine with malonic acid gave the macrocycle in a 44% yield, the same reaction with malonyl chloride, however, yielded only 3.6% of the desired product. Boc deprotection and removal of the trifluoroacetate salts gave access to the final product, 1,4,7,10,13-pentaazacyclohexadecane-14,16-dione, in an overall yield of 33%. Georg Thieme Verlag Stuttgart. 
1,4,7,10,13-pentaazacyclohexadecane-14,16-dione; Azamacrocycles; Cyclization; Ligands; Protecting groups